Adding gesture to spoken instructions makes those instructions more effective. The question we ask here is why. A group of 49 third and fourth grade children were given instruction in mathematical equivalence with gesture or without it. Children given instruction that included a correct problem-solving strategy in gesture were significantly more likely to produce that strategy in their own gestures during the same instruction period than children not exposed to the strategy in gesture. Those children were then significantly more likely to succeed on a posttest than children who did not produce the strategy in gesture. Gesture during instruction encourages children to produce gestures of their own, which, in turn, leads to learning. Children may be able to use their hands to change their minds.